P-block elements

Elements belonging to the group 13 ( i.e group IIIA ) to group 17 ( i.e group VIIA ) of the

periodic table along with the group 18 i.e the zero group elements together form the p-

block of the periodic table. 

In the p-block elements the last electron enters the outermost p orbital. They have 3 to 8

electrons in the outermost shell. As we know that the number of p orbitals is three and,

therefore, the maximum number of electrons that can be accommodated in a set of p

orbital’s is six. Hence there are six groups of p-block elements in the periodic table

numbering from 13 to 18. The First group of the p-block i.e the group IIIA is commonly

called as Boron group, the second group i.e the group IVA is called Carbon group, the

third group i.e the group VA is called Nitrogen group, the fourth group i.e the group VIA is

called Chalcogens,t he fifth group i.e the group VIIA is called Halogens and 

the sixth group i.e the zero group or group 18 is called Inert or Noble gases group. In the

p-block all the three types of elements are present, i.e. the Metals, on-Metals and

Metalloids .The zigzag line in the p-block separates all the elements that are metals from

those that are non-metals. Metals are found on the left of the line, and non-metals are

those on the right. Along the line we find the 

metalloids. Due to the presence of all types of elements the p-block shows a lot of

variation in properties. 

Classification of elements in the p-block of the Periodic Table :- The elements in the p-

block of the periodic table consists of all types of elements i.e metals , non-metals and

metalloids. 

a) Metals :- 1)Aluminium, 2)Gallium, 3)Indium, 4)Thallium, 5)Tin, 6)Lead, 7)Bismuth  

b)Non-Metals :- 1)Helium, 2)Carbon, 3)Nitrogen, 4)Oxygen, 5)Fluorine,

6)Neon, 7)Phosphorus, 8)Sulphur, 9)Chlorine, 10)Argon, 11)Selenium, 12)Bromine,

13)Krypton, 14)Iodine, 15)Xenon, 16) Radon. 

c) Metalloids:- 1)Boron, 2)Silicon, 3)Germanium, 4)Arsenic, 5)Antimony,

6)Tellurium, 7)Polonium, 8)Astatine. 

Characteristic Properties of elements in p-block of Modern Periodic Table :- 

1) Electronic Configuration:- The general valence shell electronic configuration of p-block

elements is ns 2 np 1-6 (except for He). The inner core of the electronic configuration

may, however, differ. 

The General electronic configuration shown by elements from group13 to 

18 of p-block is as given below: - 

Group 13 (Boron family):- ns 2 np 1. 

Group 14 (Carbon family):- ns 2 np 2. 

Group 15 (Nitrogen family):- ns 2 np 3. 

Group 16 (Oxygen family):- ns 2 np 4. 

Group 17 (Halogen family):- ns 2 np 5. 

Group 18 (Noble gases):- ns 2 np 6 (except Helium). 

The general electronic configuration of Helium is 1s 2. Due to their distinct electronic

configuration p-block elements show a lot of variation in properties. 

2) Metallic Character:- As stated earlier p-block contains all types of elements i.e metals,

on-metals and metalloids . The p-block is the only region of the periodic table to contain

metalloids. The non metallic character decreases down the group whereas there is a

gradual increase in non-metallic character from left to right in the p-block. The metallic

character tends to increase down each group whereas it decreases as we go from left to

right across a period. In fact, the 

heaviest element in each p-block group is the most metallic in nature. 

3) Atomic Density:- The Atomic Density of elements in p-block increases down the group,

this is due to increase in the size of the atom down the group. Whereas it decreases as

we move from left to 

right across the period, this is due to the decrease in atomic size of all elements in the p-

block across the period. Of all the elements, aluminium is of very low density and is

widely used as a structural material. 

4) Melting and Boiling points: - The Melting and Boiling points gradually increases down

the group because the molecular mass increases down the group and hence the

intermolecular forces 

increases. 

5) Oxidation state:- The p-block elements show a variable oxidation state . The oxidation

states increases as we move from left to right in the periodic table. The maximum

oxidation state shown by a p-block element is equal to the total number of valence

electrons. According 

to this, the oxidation states shown by different groups is as follows :- 

Boron family (Group 13) :- +3 

Carbon family ( Group 14) :- +4 

Nitrogen family (Group 15) :- +5 

Oxygen family ( Group 16) :- +6 

Halogen family (Group 17) :- +7 

Noble gases ( Group 18) :- +8 

But in addition to this p-block elements may also show other oxidation states which

normally , but not necessarily , differ from total number of valence electrons by unit of

two. The other oxidation state two unit less than the group oxidation state shown by

different groups is as follows :- 

Boron family (Group 13) :- +1 

Carbon family ( Group 14) :- +2 , -4 

Nitrogen family (Group 15) :- +3, -3 

Oxygen family ( Group 16) :- +4, +2, -2 

Halogen family (Group 17) :- +5, +3, +1, -1 

Noble gases ( Group 18) :- +6, +4, +2 . 

However, the relative stabilities of these two oxidation states i.e the group oxidation

state and the other oxidation state two unit less than the group oxidation state , may

vary from group to group . 

6) Atomic and Ionic radii:- As we move down the group in the p-block one extra shell than

the preceding element gets added into the next element. This ultimately increases the

atomic and the ionic radius of every next element down the group, which finally shows

that the atomic and the ionic radii increases down the group. The trend, is not same

across the period. As we move from left to right in a period the Atomic radii and the Ionic

radii of p-block elements decreases. The 

Atomic radius increases greatly from Boron to Aluminum. This increase is due to greater

screening effect caused by the eight electrons present in the penultimate shell. 

7) Electrode Potential :- The p-block elements generally have a positive electrode

potential. It generally decreases down the groups. 

For eg. Consider the electrode potentials of the halogen group: - 

Fluorine = 2.87 V 

Chlorine = 1.36 V 

Bromine = 1.09 V 

Iodine = 0.53 V 

From the above analytical data we can say that the electrode potential in the p-block

decreases down the groups. 

8) Ionisation Energies: - The p-block elements have high ionization potentials. The

ionisation energies of p-block elements increases from left to right in a period due to

increasing effective nuclear charge. According to the general trends the ionisation

energy values decreases 

down the group but do not decrease smoothly as expected. Non-metals have high

Ionisation Energies than metals. It is maximum for a noble gas because noble gases have

completely filled configuration. Some elements at the bottom of a group like Lead, Tin,

Thallium, Bismuth, 

etc. behaves almost as a metal with very low ionization energies. 

9) Magnetic Properties: - The elements Radon, Astatine, Iodine and Polonium of the p-

block are Non-Magnetic in nature. The element Tin is Paramagnetic and the rest all

elements of the p-block are Diamagnetic in nature. 

10) Complex Formation :- The smaller size and the greater charge of the elements of

different groups of p-block enable them to have a greater tendency to form complexes

than the s-block elements. The complex formation tendency decreases down the group

as the size of the atoms increases down the group. 

11) Chemical Reactivity:- The Chemical Reactivity of elements in the p-block increases as

we move from left to right in a period. But as we move down in a group the chemical

reactivity of elements decreases down the group. 

i) Reactivity of Noble gases :- All the orbitals of the noble gases are completely filled by

electrons and it is very difficult to break their stability by the addition or removal of

electrons. Thus the noble gases exhibit very low chemical reactivity. Because of their low

reactivity noble gases, are often used when an nonreactive atmosphere is needed, such

as in welding. 

Preceding the noble gas family there are two chemically important groups of non-metals.

They are the halogens (Group 17) and the chalcogens (Group 16). These two groups of

elements have high electron gain enthalpies and can readily add one or two electrons

forming an anion to attain the stable noble gas configuration thus showing

good chemical reactivity. 

ii) Reactivity of Halogens :- 

a) All halogens are naturally found in a combined state. 

b) Fluorine reacts readily with almost any substance coming in contact with it. 

c) Chlorine, Bromine, and Iodine are progressively less reactive but 

still form compounds with most other elements, especially metals. 

d) All the halogens are strong oxidising agents. The halogens oxidize 

other Substances, but themselves get reduced. 

e) All halogens combine directly with sodium to form sodium halides. 

f) All halogens react with red phosphorus to form phosphorus halides. 

g) Halogens react readily with alkali metals forming salts. 

h) The presence of Chlorine, Bromine and Iodine can be tested by the treatment of

acidified silver nitrate solution. 

iii) Reactivity of group VIA Elements ( Chalogens ) :-  

a) As we approach to the right-hand side of the periodic table, similarities among the

elements within a group become greater. This is true for the group VIA. Except Polonium,

which is radioactive and usually omitted from all discussions. 

b) All members of the group VIA form X 2– ions when combined with highly

electropositive metals. 

c) The tendency to be reduced to the - 2 oxidation state decreases significantly from top

to bottom. 

d) At ordinary temperatures and pressures, oxygen is a gas. It exists in either of the two

allotropic forms :- O 2 , which makes up 21 percent of the earth's atmosphere, or O 3

(ozone), which slowly 

decomposes to O 2 . 

e) The ozone itself absorbs longer-wavelength ultraviolet radiations, preventing these

harmful rays from reaching the earth's surface which would otherwise increase the

probability of human skin cancer and can also cause other environmental problems. 

f) The Compounds of selenium and tellurium are of little commercial importance as they

are toxic. 

iv) Reactivity of Metalloids :- 

a) The chemical reactivity of the metalloids depends on the substance with which it is

reacting. For example:- Boron behaves as a non metal when reacting with sodium, but it

acts as a metal when reacting with fluorine . 

b) Thus from the above example we can say that Metalloids show variable chemical

properties. 

c) They act like non-metals when they react with metals whereas they act like metals

when they react with non-metals. 

d) Due to their low electro negativity, they are usually oxidized in reactions. The oxides

of metalloids are usually amphoteric. 

v) Reactivity of group VA Elements :- 

a) All the group VA elements form trihydrides when reacted with hydrogen. 

b) The reactivity decreases down the group. 

c) The elements in the group VA either form trioxides or pentoxides when reacted with

oxygen. 

d) Also they form trihalides or pentahalides when reacted with halogens. 

e) All the group VA elements react with metals to form binary compounds. 

f) The most important compounds of the group VA elements are those of nitrogen and

phosphorus. 

g) Nitrogen and phosphorus are most commonly used as fertilizer. 

vi) Reactivity of group IIIA Elements :- 

a) Unlike groups IA and IIA, none of the group IIIA elements react directly with hydrogen

to form hydrides. 

b) Also all the group IIIA elements react with halogens to form trihalides instead of simply

halides like group IA and IIA elements. 

vii) Reactivity of group IVA elements :- 

a) Carbon have a ability to form strong bonds with other carbon atoms and thus form a

tremendous variety of organic compounds 

b) In the +4 oxidation state lead acts as a strong oxidizing agent, gaining two electrons

and after gaining electrons it gets reduced to the +2 oxidation state. 

c) Also in the +4 oxidation state lead forms covalent compounds and bonds strongly to

carbon. 

d) Besides the metals themselves, some tin and lead compounds are of commercial

importance. For eg :- Tin(II) fluoride (stannous fluoride), is added to some toothpastes to

inhibit dental cares. 

e) Lead is also found in two main commercial applications. One, the lead-acid storage

batteries used to start cars and the other is in the automobile fuel. 

12) Conductivity :- The conductivity of elements in p-block increases down the group.

Generally the metals in the p-block are good conductors of heat and electricity whereas

the non-metals are poor 

conductors of heat and electricity. The conductivity of metalloids lies in between the

metals and non-metals. 

13) Colour :- 

Colour of group IIIA elements :- 

All the group IIIA elements are silvery solids except boron which is brown solid. 

Colour of group IVA elements: - 

Carbon is black in colour whereas silicon and germanium have reddish brown or dull grey

or black colour. Lead has a bluish-white colour. 

Colour of group VA elements: - 

Nitrogen is a colourless. 

Phosphorus exists in white colour. 

Arsenic is found in yellow and grey solid form. 

Antimony is found in a amorphous grey form. 

Bismuth is silvery white in colour. 

Colour of group 16 elements :- 

Oxygen is a gas and is colourless . 

Sulphur is pale yellow in colour. 

Tellurium is Silvery-white in colour. 

All the Halogens are coloured. They have following colours: - 

Fluorine: - Pale yellow/Chlorine: - Greenish yellow/Bromine: - Reddish brown

Iodine: - Violet black. 

Noble Gases have following colours: - Helium is red, Neon is orange, Krypton is purple

whereas Xenon is white in colour. Radon is colourless. 

14) Flame colouration: - Not all but a few p-block elements impart characteristic colour to

the flame. Arsenic impart Blue colour to the flame. Boron imparts Bright green Colour to

the flame. Copper (I) impart Blue colour whereas Copper (II) (non-halide) impart

Green colour to flame whereas Copper (II) (halide) impart Blue- green colour to flame.

Indium and selenium impart Blue colour to flame. Phosphorus impart Pale bluish green

colour whereas Lead impart Blue/White colour to flame. Antimony and Tellurium impart

Pale green colour. Thallium impart Pure green colour to flame. 

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Nitrogen has the least tendency to form compounds in +5 oxidation state due to the fact that it does not have a vacant d-orbitals.

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Tip #12The decreasing order of catenation amongst [group 16] elements is S > Se > O > Te

Tip #13Tendency for catenation decreases in the order P>N>As>Sb>Bi [GROUP-15]

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